The present invention is directed generally to injection molding machines having a stripper for stripping molded articles from the mold core subsequent to removal of the article from the mold cavity, and particularly to means for adjusting the position and/or timing of release of the molded article from the stripper.
Injection molding machines commonly include a fixed platen which is generally fixed at a specific location with respect to the base of the injection molding machine. This fixed platen can take the form of a mold base and can include the runner or manifold system coupled between the mold base and a plasticizing injector unit. The mold base and/or fixed platen generally includes one or more mold cavity units which, together with a core unit, defines a space into which molten plastic is injected to form one or more articles. The core units are movable with respect to the base and are generally mounted on a movable platen which reciprocates with respect to the fixed platen between a closed position where the core unit and cavity unit are engaged with each other to define the molding space and an open position where the plastic article can be removed from the molding machine.
Molding machines also often include a stripper for stripping the molded articles from the core or cavity unit. In some instances, the stripper takes the form of some additional space defining surfaces which act together with the mold cavity and mold core to define the space receiving plastic material from the injection unit. The space defining surfaces on the stripper are generally designed to intimately engage the molded article so the article can be successfully removed from the core and cavity assemblies and additionally require some action to affirmatively cause release of the molded article from the space defining surfaces. The successful operation of this stripping and plastic part release has been the subject of some prior development.
In order to have the space forming surfaces release the molded article once it has been successfully stripped from the core and cavity unit, the space defining surfaces have been coupled to an actuating means as shown in U.S. Pat. No. 4,497,624. The space defining surfaces are there disclosed to constitute thread splits for forming threads on a portion of each molded article with each of the thread splits being coupled to an actuator for causing relative movement of the thread splits. The actuator is in turn coupled to cam followers which ride within a track. The track includes an insert which defines a ramp or incline which, interacting with the cam followers, causes the actuator to move the thread splits engaging the molded article in such a way to release the article. In use, at least two, and typically four, such track inserts are employed and are adjustable in position with respect to the track to permit adjustment of the timing and/or point of release of the molded article. The adjustability of the position of the track inserts itself caused some difficulty in that it is difficult to position all four track inserts at the same relative position in the respective tracks to cause a balanced application of force to move the thread splits apart, the imbalance of force results in an unintended strain and wear on the equipment and led to unreliable part separation.
The use of a single fixed position ramp or incline fails to permit the variability in operation of the mold unit thought to be desirable in that changes in the confirmation of the core and cavity unit can also require changes in the part release point. Thus, the use of single position ramps or inclines to activate the actuators by means of the cam followers is not a viable alternative. It was therefore desirable to develop apparatus interactive with a cam coupled to an actuator for causing release of parts from a molding machine which cam would be adjustable in position yet easily coordinated with other like cams on the same machine to avoid any unbalanced application of force and would improve part drop performance.